In heart failure, the heart is unable to pump enough blood to meet your body’s requirements. As a result, excess fluid begins to build up in the body’s blood vessels, which can leak into the pleural layer outside the lungs, termed pleural effusion. This can cause shortness of breath. Swelling of the lower limbs occurs. As less blood being pumped to the body, common symptoms include dizziness and lethargy. Ejection fraction (which is a calculation obtained from an echocardiogram) is a measure of the amount of blood pushed in and out with each heartbeat, as a percentage. An EF of over 52% is considered normal. You can still have heart failure even if the EF is in the normal range. This is known as heart failure with preserved ejection fraction (HFpEF). Heart failure usually occurs as a result of the heart muscle becoming damaged from a heart attack, and causes it to become enlarged and stiff.

For more information on heart failure.
What is heart failure | The Heart Foundation